A new variety of Dasya rigidula (Kutzing) Ardissone is reported from the Sea of Japan. The female reproductive structure and the development of the carposporophyte are newly reported for the species. Rarely two procarps per segment in this new variety is a unique character among the known species of the genus Dasya.
Thalli are brownish red, 0.3-2 cm in height. The main axes are 0.3-2.3 mm in diameter, lower pericentral cells are 40-70 μ m in diameter, 107-227 μ m in length. The axes usually have no cortication. Pseudolaterals are 1-3.3 mm in length, branching 2-3 times, arranged radially or bilaterally on the indeterminate axes. Procarps are one rarely two per segment, arranged spirally. Two gonimolobes are formed in the cystocarp. Connecting cell is one. The third carpogonial branch cell is small or large. Mature pericarp is two- or three-cell-layered. Mature cystocarps are c. 0.3 mm in diameter. Spermatangial stichidia are simple or branched. Tetrasporangial stichidia are more or less curved to one side and simple, sometimes bifurcate, 130-270 X 280-530 μ m. Mature tetrasporangia are up to 57 μ m in diameter